As the size of conventional transistors is decreased, the characteristics of the device may be adversely affected. For example, transistors may experience a short channel effect. Referring now to FIG. 1, a cross-section illustrating conventional transistors will be discussed. As illustrated, conventional transistors may include a gate insulation layer 14 on an integrated circuit substrate 10. A gate electrode 16 may be provided on the gate insulation layer 14. Source and drain regions 12 may be formed in the integrated circuit substrate 10 by implanting impurities in the integrated circuit substrate 10 adjacent both sides of the gate electrode 16. Regions between the source and drain regions 12 define channel regions of the transistor.
In conventional transistors illustrated in FIG. 1, when a length of the channel is decreased, the influence of the source and drain regions on the channel region may increase. Accordingly, a short channel effect, for example, a change of a threshold voltage, an increase in a leakage current and/or a punch-through between the source and drain regions may occur. The reduction in size of conventional transistors may be limited by the occurrence of the short channel effect. Therefore, highly integrated devices may be difficult to fabricate.
Conventional silicon-on-insulator (SOI) transistors may reduce the likelihood of the occurrence of the short channel effect. Referring now to FIG. 2 a cross section of conventional SOI transistors will be discussed. As illustrated, a gate insulation layer 26 is provided on a SOI layer 25. The SOI layer is provided on a buried insulation layer 22 and the buried insulation layer 22 is provided on the integrated circuit substrate 10. A gate electrode 28 is formed on the gate insulation layer 26. Source and drain regions 24 are provided in the SOI layer by implanting impurities in the SOI layer 25 adjacent both sides of the gate electrode 28. Regions between the source and drain regions 24 define channel regions of the transistor.
As illustrated in FIG. 2, a source and/or drain junction of the SOI transistor contacts the buried insulation layer 22. Accordingly, a depletion layer of the source and/or drain junction may be suppressed so that a short channel effect and/or a leakage current may possibly be reduced. However, a floating body effect may occur in SOI transistors because the SOI layer 25 is isolated by the buried insulation layer 22 and an isolation layer. Thus, dispersion of heat generated from operating integrated circuit devices may be difficult and manufacturing costs may be increased. Accordingly, improved integrated circuit devices may be desired.